Multi-source far-field radiation suppression method based on equivalent dipole method

Abstract

This invention discloses a multi-source far-field radiation suppression method based on the equivalent dipole method, mainly addressing the problems of existing methods such as excessively long modeling time, long scanning time for closed electromagnetic field information, and inapplicability to multi-device systems. This invention calculates the equivalent dipole model of the radiation source using the magnetic field information of the radiation source and the position coordinates of the scanning plane and the radiation source. By changing the coordinate information to the far field, the far-field vertical electric field of the equivalent dipole model is quickly obtained. Furthermore, by changing the coordinate information of the dipole model, the equivalent device rotation is achieved, thereby obtaining the optimal placement angle of the device. This invention optimizes the placement angle of the radiation source by establishing an equivalent dipole model and rotating it. Compared with existing methods, this invention improves both application scenarios and efficiency.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic technology, and more specifically relates to a multi-source far-field radiation suppression method based on the equivalent dipole method in the field of electromagnetic compatibility technology. This invention can be applied to optimize the angular placement of multiple devices in an electronic system to suppress their far-field radiation. Background Technology

[0002] Electromagnetic compatibility (EMC) issues in electronic systems are becoming increasingly serious with the continuous increase in device integration. EMC refers to the ability of electronic equipment or systems to operate normally in their electromagnetic environment without causing unacceptable electromagnetic interference to any other equipment in that environment. Excessive EMC can lead to malfunctions of electronic equipment or even the entire electronic system, thus affecting its safety and reliability. Furthermore, with increasingly stringent requirements for the electromagnetic interference immunity (EMS) of electronic equipment and systems, suppressing device EMC has become a crucial issue to consider in the EMC design of electronic equipment and systems.

[0003] The traditional PCB EMC design flow is PCB design—test circuit—EMC testing—production. Engineers often rely heavily on rules of thumb in PCB design, such as overall PCB layout and routing, power supply design, grounding design, and shielding design. PCB-related EMC design cannot be evaluated and optimized during the design process, often requiring repeated modifications or even redesign to pass EMC tests. Therefore, modeling, simulating, and analyzing the electromagnetic interference characteristics of the PCB during the design phase is crucial. PCBs designed based on this analysis can pass EMC tests more quickly and meet relevant EMC standards, shortening the design cycle and saving costs. With the development of high-performance computers, full-wave analysis methods based on numerical analytical methods of electromagnetic fields have become increasingly important. Full-wave analysis is also applicable to PCB EMI / EMC issues, and commercial simulation software such as HFSS is already essential software for EMC engineers. However, full-wave analysis has its limitations; for more complex devices, full-wave simulation requires excessive time. Using full-wave simulation requires initial device modeling, which necessitates engineers spending considerable time on model building and parameter / excitation settings. Furthermore, due to the complexity and high integration of the devices, the computation time and memory requirements of this method are constantly increasing.

[0004] J. Pan of the EMC Lab at Missouri University of Science and Technology, Rolland, proposed a reciprocity-based decomposition method for far-field radiation prediction in his paper "Far-field Prediction by Only Magnetic Near Fields on a Simplified Huygens's Surface". This method predicts far-field radiation between devices by separately measuring the closed near-field electromagnetic field data of the radiation source and the radiated device, and then calculating using a finite element method. When measuring the near-field data of the device, a vector network analyzer or spectrum analyzer is typically used to measure the amplitude and phase information of the electric and magnetic fields around the device. To ensure the measurement data satisfies closure, six planes are typically measured for both the radiation source and the radiated device. This method can directly solve for the magnitude of the far-field radiation signal received by the radiated device, thereby guiding the optimization of subsequent EMC design. The limitations of this method are: firstly, it requires complete measurement of the closed electromagnetic field information of both the radiation source and the radiated device, which not only results in long measurement times and low computational efficiency, but also poor applicability to devices with complex spatial arrangements. Second, this method is only applicable to point-to-point radiation and does not consider the overall far-field radiation of multi-device systems, thus limiting its application scenarios. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a multi-source far-field radiation suppression method based on the equivalent dipole method. This method solves problems such as excessively long modeling time, lengthy scanning time for closed electromagnetic field information, and unsuitability for multi-device systems.

[0006] The approach to achieving the objective of this invention is as follows: The amplitude and phase of the magnetic field at each sampling point are measured on a near-field scanning plane located above the radiation source. For multi-device systems, each radiation source needs to be individually excited, or the remaining devices need to be shielded using shielding material, thus enabling separate measurements of multiple radiation sources. Based on the magnetic field information obtained from the scan, as well as the position coordinates of the scanning plane and the radiation source, the dipole radiation formula is inverted to calculate the amplitude and phase of the dipole array. By changing the coordinate information to the far field and substituting it into the dipole array radiation formula, the far-field vertical electric field of the equivalent dipole model of a single device, i.e., its far-field radiation, can be quickly obtained. After performing the above operations on all devices in the system, the coordinate information of the dipole model is changed to achieve the effect of equivalent device rotation, and the far-field vertical electric field at all angles is calculated, thereby determining the optimal placement angle of the device.

[0007] The specific steps to achieve the objective of this invention are as follows:

[0008] Step 1: Select an unselected radiation source, turn off the other radiation sources, and measure the magnetic field H in the x-direction on the plane directly above the selected radiation source.x and the magnetic field H in the y direction y The magnitude and phase of the radiation source are used to obtain the magnetic field matrix of the radiation source;

[0009] Step 2: Record the coordinates of all scanning points within the measurement plane;

[0010] Step 3: Take points within the selected radiation source area and record the coordinates of all points.

[0011] Step 4: Construct a transmission matrix that characterizes the relationship between the radiation source and the radiation field;

[0012] Step 5: Generate an equivalent dipole model of the radiation source;

[0013] Step 6: Calculate the far-field vertical electric field for each dipole;

[0014] Step 7: Accumulate the far-field vertical electric fields of all dipoles of the selected radiation source to obtain the far-field vertical electric field of the equivalent dipole model of the radiation source.

[0015] Step 8: Determine if all radiation sources have been selected. If yes, proceed to step 9; otherwise, proceed to step 1.

[0016] Step 9: Determine the optimal angle for the multi-source model:

[0017] Calculate the equivalent dipole model X of the radiation source k_rotate The magnetic dipole after each rotation; substitute the coordinates corresponding to the equivalent dipole model of the radiation source after each rotation into the formula in step 6 to recalculate the far-field vertical electric field after each rotation; superimpose the far-field vertical electric fields of all radiation sources under all angle combinations; select the placement angle of the radiation source corresponding to the minimum cumulative far-field vertical electric field as the optimal placement angle of the radiation source.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] First, this invention only requires measuring the magnetic field information of a single plane above the electronic device, including the amplitude and phase of the magnetic field. Compared with the existing decomposition method based on the reciprocity theorem, this greatly reduces the number of measurements, giving this invention the advantages of shorter measurement time and more applicable scenarios, thereby shortening the overall EMC design process.

[0020] Secondly, this invention equates the radiation source to a dipole model. Relying on the simplicity and versatility of the dipole model, it requires less time and memory compared to traditional simulation software when calculating far-field radiation, thus improving the computational efficiency of this invention. Furthermore, the dipole array model can be imported into simulation software, thereby saving modeling time compared to traditional simulation methods.

[0021] Third, this invention applies the equivalent dipole method to the modeling and far-field prediction of multi-device systems. By optimizing the placement of multiple electronic devices in the system, it reduces the far-field radiation of the multi-device system and overcomes the limitation of the decomposition method based on the reciprocity theorem, which is only applicable to point-to-point radiation. Attached Figure Description

[0022] Figure 1 This is a flowchart of the present invention;

[0023] Figure 2 This is a scene diagram illustrating the magnetic field measurement method of the present invention.

[0024] Figure 3 This is a schematic diagram of the dipole equivalent model of the present invention;

[0025] Figure 4 This is a schematic diagram of the patch antenna rotation according to an embodiment of the present invention;

[0026] Figure 5 This is a simulation diagram of the present invention. Detailed Implementation

[0027] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0028] Reference Figure 1 The implementation steps of the embodiments of the present invention will be further described below.

[0029] Step 1: Select an unselected radiation source, turn off the other radiation sources, and measure the magnetic field H in the x-direction on the plane directly above the selected radiation source. x and the magnetic field H in the y direction y The magnitude and phase of the radiation source are used to obtain the magnetic field matrix of the radiation source.

[0030] The aforementioned shutting down of other radiation sources refers to using shielding materials to shield other radiation sources that cannot be shut down.

[0031] The area of ​​the plane directly above the selected radiation source for the measurement should be larger than the area of ​​the radiation source.

[0032] When measuring the magnetic field of the plane directly above the selected radiation source, the measurement interval should be less than 1 / 2λ, where λ is the wavelength of the selected radiation source.

[0033] Reference Figure 2 In this embodiment, two patch antennas are used. First, the center patch antenna is selected and fed. The magnetic field probe is connected to the scanning arm, and then connected to the vector network analyzer. The magnetic field probe is placed 20mm above the device under test, and a robotic arm is used to control the probe to move horizontally within this plane. The vector network analyzer records data at regular intervals. In this embodiment, the scanning interval is 10mm.

[0034] Step 2: Record the coordinates of all scanning points within the measurement plane. (Refer to...) Figure 3 In this embodiment, the scanning plane of the device is the blue area in the figure, and points are taken from it at a scanning interval of 10 mm.

[0035] Step 3: Within the selected radiation source area, take points and record the coordinates of all points. (Refer to...) Figure 3 In the embodiment, the radiation source area is the yellow area in the figure. Points are taken at 1mm intervals within this area and their coordinates are recorded.

[0036] Step 4, construct the transfer matrix T representing the relationship between the radiation source and the radiation field as follows:

[0037]

[0038] Where T HxPz T HxMx T HxMy T HyPz T HyMx T HyMy These represent the magnetic fields H of different types of dipoles in the x-direction. x magnetic field H in the y direction y The transmission relationships are obtained from the following formulas:

[0039]

[0040]

[0041]

[0042]

[0043]

[0044]

[0045] Where i is the i-th scan point, and j is the j-th dipole. x, y, z are the coordinates of the measurement plane, x', y', d are the coordinates of the radiation source, and k0 is the propagation constant.

[0046] Step 5: Generate the equivalent dipole model of the radiation source. The specific steps are as follows:

[0047] The first step is to obtain the maximum value H of the measured magnetic field amplitude of the selected radiation source. max Substituting into the following formula, we obtain the normalized magnetic field data:

[0048]

[0049] Among them, F norm This is the normalized magnetic field data.

[0050] The second step is to normalize the transmission matrix T obtained in step 2 using the following formula to obtain the normalized transmission matrix:

[0051]

[0052] Among them, T nk Normalized transfer matrix;

[0053] The third step is to solve for the equivalent dipole model of the radiation source using the following formula:

[0054] X k =[T′ nk T nk ] -1 T′ nk F norm

[0055] Among them, X k The equivalent dipole model for the radiation source.

[0056] Reference Figure 3 The equivalent dipole model is the array of arrows shown in the figure.

[0057] Step 6, calculate the far-field vertical electric field of each dipole using the following formula:

[0058]

[0059] Among them, E z The far-field vertical electric field is represented by j (the imaginary unit symbol), η0 (the vacuum wave impedance), π (pi), x and y (the coordinates of all points taken within the defined far-field region), x' and y' (the coordinates of the selected radiation source), and g1, g2, g3 and r1, r2 (coordinate functions). z M x M y These are the z-direction electric dipole, the x-direction magnetic dipole, and the y-direction magnetic dipole, respectively.

[0060] Wherein, g1, g2, g3 and r1, r2 are obtained by the following formulas:

[0061]

[0062] r1=[(x-x') 2 +(y-y') 2 +(zd) 2 ] 1 / 2

[0063] r2=[(x-x') 2 +(y-y') 2 +(z+d) 2 ] 1 / 2

[0064] Where r is a coordinate function composed of r1 and r2.

[0065] Step 7: Accumulate the far-field vertical electric fields of all dipoles of the selected radiation source to obtain the far-field vertical electric field of the equivalent dipole model of the radiation source.

[0066] Step 8: Determine if all radiation sources have been selected. If yes, proceed to step 9; otherwise, proceed to step 1.

[0067] Since the center patch antenna has already been selected in this embodiment, the next step is to perform step 1 and select the right patch antenna.

[0068] Step 9: Determine the optimal angle for the multi-source model:

[0069] Calculate the equivalent dipole model X of the radiation source k_rotate The magnetic dipole after each rotation; substitute the coordinates corresponding to the equivalent dipole model of the radiation source after each rotation into the formula in step 6 to recalculate the far-field vertical electric field after each rotation; superimpose the far-field vertical electric fields of all radiation sources under all angle combinations; select the placement angle of the radiation source corresponding to the minimum cumulative far-field vertical electric field as the optimal placement angle of the radiation source.

[0070] Among them, the equivalent dipole model X of the radiation source is calculated. k_rotate The magnetic dipole after each rotation is obtained by the following equation:

[0071]

[0072]

[0073] Among them, M x_rotated_n and M y_rotated_n These are the x-direction magnetic dipole and y-direction magnetic dipole after the nth rotation, respectively. Let be the angle of the nth rotation of the equivalent dipole model of the radiation source.

[0074] The effect of rotating the right patch antenna counterclockwise by 30 degrees is as follows Figure 4 As shown.

[0075] The effects of the present invention will be further explained below in conjunction with measurement experiments and simulation experiments.

[0076] 1. Simulation experimental conditions:

[0077] The hardware platform for the simulation experiment of this invention is: AMD R5600G CPU with a main frequency of 3.9GHz and 16GB of memory.

[0078] The software platform for the simulation experiment of this invention is: Windows 10 operating system, Matlab 2023 and electromagnetic simulation software HFSS 2022R1.

[0079] 2. Simulation Experiment Content and Result Analysis:

[0080] The simulation experiment process of this invention is as follows: A CAD model of two patch antennas placed perpendicularly to each other is established using HFSS electromagnetic simulation software, as shown below. Figure 2 As shown. With two antennas excited separately, the field solver was used to obtain the magnetic field data for a 160mm*160mm area 20mm above the antennas. The coordinates of points in this plane were recorded at 10mm intervals. Points were taken within the selected patch antenna area at 1mm intervals, and the coordinates of all points were recorded. The equivalent dipole model of the antenna was calculated using Matlab 2023, and then rotated. The far-field vertical electric field after rotation was calculated. The far-field vertical electric fields of all radiating sources under all angle combinations were superimposed, and the placement angle of the radiating source corresponding to the minimum accumulated far-field vertical electric field was selected as the optimal placement angle of the radiating source.

[0081] The simulation results of the far-field vertical electric field of the above model after rotation using HFSS software and the prediction results of the far-field vertical electric field of the model after rotation using the method of the present invention are as follows: Figure 5 As shown.

[0082] The following is combined with Figure 5 The simulation diagrams further illustrate the effects of the present invention.

[0083] Figure 5 The horizontal axis represents the angle of counterclockwise rotation of the right antenna around its own center axis, in degrees, and the vertical axis represents the accumulated far-field vertical electric field, in millivolts per meter. Figure 5 The solid line in the figure represents the curve plotted from the HFSS simulation results, while the dashed line represents the curve plotted from the prediction results of the equivalent dipole model described in this invention.

[0084] Depend on Figure 5 It can be seen that the minimum far-field vertical electric field simulated by HFSS is 207 mV / m, corresponding to an angle of 89 degrees, while the minimum far-field vertical electric field predicted by the equivalent dipole model is 205 mV / m, corresponding to an angle of 106 degrees. The minimum far-field vertical electric fields of the two differ by only 2 mV / m, and the optimal angle differs by only 17 degrees. Figure 5 It can be seen that when the right antenna is not rotated, its far-field vertical electric field is 274 millivolts per meter, while the far-field vertical electric field is significantly reduced after rotating 106 degrees.

[0085] from Figure 5 As can be seen from this, the present invention can accurately predict the far-field radiated electric field of an electronic system and predict its optimal placement angle, effectively suppressing its far-field radiation.

Claims

1. A method for suppressing multi-source far-field radiation based on the equivalent dipole method, characterized in that, The magnetic field information of the plane above the radiation source is measured, and the radiation source is equivalent to a dipole model. The optimal placement angle of multiple radiation sources is solved by rotating the dipole model. The specific steps of this suppression method are as follows: Step 1: Select an unselected radiation source, turn off the other radiation sources, and measure the magnetic field in the x-direction on the plane directly above the selected radiation source. and the magnetic field in the y direction The magnitude and phase of the radiation source are used to obtain the magnetic field matrix of the radiation source; Step 2: Record the coordinates of all scanning points within the measurement plane; Step 3: Take points within the selected radiation source area and record the coordinates of all points. Step 4: Construct a transmission matrix that characterizes the relationship between the radiation source and the radiation field; Step 5: Generate an equivalent dipole model of the radiation source; Step 6, calculate the far-field vertical electric field of each dipole: ； in, The far-field perpendicular electric field, where j is the symbol for the imaginary unit. Let be the propagation constant. For vacuum wave impedance, Pi These represent the coordinates of all points taken within a defined far-field region. These are the coordinates of the selected radiation source. and Both are coordinate functions. These are, respectively, an electric dipole in the z-direction, a magnetic dipole in the x-direction, and a magnetic dipole in the y-direction; Step 7: Accumulate the far-field vertical electric fields of all dipoles of the selected radiation source to obtain the far-field vertical electric field of the equivalent dipole model of the radiation source. Step 8: Determine if all radiation sources have been selected. If yes, proceed to step 9; otherwise, proceed to step 1. Step 9: Determine the optimal angle for the multi-source model: Calculate the equivalent dipole model of the radiation source The magnetic dipole after each rotation; Substitute the coordinates of the equivalent dipole model of the radiation source after each rotation into the formula in step 6 to recalculate the far-field vertical electric field after each rotation. Superimpose the far-field vertical electric fields of all radiation sources under all angle combinations, and select the placement angle of the radiation source corresponding to the minimum cumulative far-field vertical electric field as the optimal placement angle of the radiation source.

2. The multi-source far-field radiation suppression method based on the equivalent dipole method according to claim 1, characterized in that, The shutdown of other radiation sources mentioned in step 1 refers to shielding other radiation sources that cannot be shut down using shielding materials.

3. The multi-source far-field radiation suppression method based on the equivalent dipole method according to claim 1, characterized in that, The area of ​​the plane directly above the selected radiation source in step 1 should be larger than the area of ​​the radiation source.

4. The multi-source far-field radiation suppression method based on the equivalent dipole method according to claim 1, characterized in that, When measuring the magnetic field of the plane directly above the selected radiation source as described in step 1, the measurement interval should be less than 1 / 2λ, where λ is the wavelength of the selected radiation source.

5. The multi-source far-field radiation suppression method based on the equivalent dipole method according to claim 1, characterized in that, The transfer matrix T, which characterizes the relationship between the radiation source and the radiation field as described in step 4, is as follows: ； in , , , , , These represent the magnetic fields of different types of dipoles in the x-direction. magnetic field in the y direction The transmission relationships are obtained from the following formulas: ； in, For the first One scan point, For the first A dipole, , These are the coordinates of the measurement plane. These are the coordinates of the radiation source. is the propagation constant.

6. The multi-source far-field radiation suppression method based on the equivalent dipole method according to claim 5, characterized in that, The steps for generating the equivalent dipole model of the radiation source in step 5 are as follows: The first step is to take the maximum value of the measured magnetic field amplitude of the selected radiation source. Substituting into the following formula, we obtain the normalized magnetic field data: ； in, The data is the normalized magnetic field data; The second step is to normalize the transmission matrix T obtained in step 2 using the following formula to obtain the normalized transmission matrix: ； in, Normalized transfer matrix; The third step is to solve for the equivalent dipole model of the radiation source using the following formula: ； in, The equivalent dipole model for the radiation source.

7. The multi-source far-field radiation suppression method based on the equivalent dipole method according to claim 6, characterized in that, The aforementioned and They are obtained from the following formulas respectively: ； ； in, For the reason The coordinate function formed.

8. The multi-source far-field radiation suppression method based on the equivalent dipole method according to claim 1, characterized in that, The calculation of the equivalent dipole model of the radiation source described in step 9 The magnetic dipole after each rotation is obtained by the following equation: ； ； in, and The first The magnetic dipole in the x-direction and the magnetic dipole in the y-direction after the second rotation For the equivalent dipole model of the radiation source, the first The angle of the next rotation.

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